Radiation therapy for treating a patient by irradiating a tumor-affected area with a therapeutic radiation ray is known in the art. A radiation therapy apparatus for performing radiation therapy includes an imager system that images a radiographic image of a patient, a therapeutic radiation ray irradiation device that irradiates the patient with a therapeutic radiation ray, and a driving device that drives the therapeutic radiation ray irradiation device. The radiation therapy apparatus calculates the position of the affected area of the patient based on the radiographic image and controls the driving device based on the calculated position so that the affected area is irradiated with the therapeutic radiation ray. That is, such radiation therapy apparatus allows irradiating the affected area with the therapeutic radiation ray even when the affected area moves in accordance with the respiration of the patient or the like.
Examples of such radiation therapy include stereoscopic moving-subject-tracking and surrogate moving-subject-tracking. The stereoscopic moving-subject-tracking is known in the art as disclosed in Japanese Patent Application Publication No. P2007-236729A, for example. The surrogate moving-subject-tracking is known in the art as disclosed in Japanese Patent Application Publication No. P2007-236730A, for example. In these types of radiation therapy, high therapeutic effect is desired, and therapeutic radiation rays are desired to cause a reduced dose for irradiation on normal cells, compared with that on cells of the affected area. Therefore, the radiation therapy apparatus is desired to irradiate the affected area with a therapeutic ray with higher accuracy and to calculate the position of the affected area with higher accuracy based on the radiographic image.
Japanese Patent Application Publication No. P2007-236729A discloses a radiation therapy apparatus controller for aligning a predetermined position of a target subject with a predetermined position of a radiation therapy apparatus with higher accuracy. The radiation therapy apparatus controller includes a therapeutic radiation ray irradiation device that emits a therapeutic radiation ray, an imager that generates an imager image of the target subject with a radiation ray passing through the target subject, and a driving device that moves a couch on which the target subject is placed with respect to the therapeutic radiation ray irradiation device. The radiation therapy apparatus controller includes a reference image generating part that collects reference imager images imaged by the imager, a radiographic image imaging part that images an imaged imager image of the target subject by the imager, and an affected area position control part that determines whether a relative position of the couch with respect to the therapeutic radiation ray irradiation device based on the position where a feature point included in the target subject is imaged in the imaged imager image and the position where the feature point is imaged in the reference imager image.
Japanese Patent Application Publication No. P2007-236730A discloses a radiation therapy apparatus controller which irradiates a part of a moving target subject with a radiation ray with an improved reliably. The radiation therapy apparatus controller includes a therapeutic radiation ray irradiation device that irradiates a part of the target subject with a therapeutic radiation ray, a motion detecting device that detects a motion of the target subject, and a driving device that moves the therapeutic radiation ray irradiation device with respect to the target subject. The radiation therapy apparatus controller includes an affected-area position database in which a set of motions are associated with a set of positions, a motion obtaining part that obtains the motion from the motion detecting device, and an irradiation position control part that moves the therapeutic radiation ray irradiation device by using the driving device so that the position associated with the motion out of the set of the positions is irradiated with the therapeutic radiation ray.
Japanese Patent Gazette No. 3,673,578 discloses a correlation-based tracking system configured to make a search in a search block provided around a reference block for a position with the highest degree of matching out of a plurality of templates of the reference block, to output data and instructions associated with the motion vector, and the matched template, and to stably achieve a tracking with high accuracy even if the shape of the subject is rapidly changed. The correlation-tracking system, which achieves tracking of the subject on the screen, includes means of setting a plurality of templates representing the changing shape and expression, including a rotation of the subject to predict the change thereof in advance, a reference block having the same size as the templates and a search block of a predetermined size around the reference block on the screen, means of sequentially matching the plurality of templates with shifts of the reference block in the search block to calculate the motion vector to the position where the degree of matching is highest, and tracking the subject while sequentially updating the position, and means that output data or instructions associated with the found template.
Japanese Patent Gazette No. 4,126,318 discloses a radiation therapy apparatus controller that detects a predetermined portion of the target subject with higher accuracy. The therapeutic apparatus controller controls a radiation therapy apparatus including a therapeutic radiation ray irradiation device that emits a therapeutic radiation ray and an imager that generates an imager image of the target subject by using a radiation ray passing through the target subject. The therapeutic apparatus controller includes a feature spot extracting part that generates a plurality of projection templates respectively representing the changes in the projection luminance in a case when a plurality of image templates are projected in one direction, which templates are different in the relation of the imaging positions of the target region of the target subject and the non-target region of the target subject, and generates a feature spot template representing a portion that is common among the plurality of projection templates; and an affected-area position calculating part that performs pattern matching on the change in projection luminance when the imager image is projected in one direction with the feature-spot template and calculates the position of the target region.
Japanese Patent Gazette No. 3,785,136 discloses a radiation therapy apparatus capable of facilitating treatment planning after radiation therapy is performed on a target subject. The radiation therapy apparatus includes a radiation-ray irradiation head that emits a therapeutic radiation ray, an image processing part that generates an image of an affected area of a target subject irradiated with the therapeutic radiation ray from the radiation-ray irradiation head, and a control part that controls the radiation-ray irradiation head and the image processing part so that cycles including generation of the image and irradiation of the therapeutic radiation ray are repeated, that the imaging of the image using the diagnostic X-ray in the second cycle following the first cycle is completed before the radiation of the therapeutic radiation ray in the first cycle, and that the processing of the imaged image during irradiation of the therapeutic radiation ray in the first cycle is completed to generate the image of the affected area.